Abstract
Introduction
Total hip arthroplasty (THA) is a common operation. Different operative approaches have specific benefits and compromises. Soft tissue injury occurs in total hip arthroplasty. This prospective study objectively measured muscle volume changes after direct anterior and posterior approach surgeries.
Methods
Patients undergoing Direct Anterior Approach (DAA) and Posterior Approach (PA) THA were prospectively evaluated. 3 orthopaedic surgeons performed all surgeries. Muscle volumes of all major muscles around the hip were objectively measured using preoperative and 2 different postoperative follow-up MRIs. 2 independent measurers performed all radiographic volume measurements. Repeated-measures ANOVA was used to compare mean muscle volume changes over time. Student's t-test was used to compare muscle volumes between groups at specific time intervals.
Results
MRIs for 10 DAA and 9 PA patients were analyzed. No significant differences between groups were found in BMI or Age. Pre-operative muscle volume comparisons showed no significant differences. Average postoperative follow-up times were 9.6 and 24.3 weeks. First follow-up showed significant atrophy for the DAA in Gluteus Medius (−7.3%), Gluteus Minimus (−17.5%), and Obturator Internus (−37.3%) muscles. Final follow-up showed significant recovery in Gluteus Medius (+12%) and Minimus (+11.1%) muscles. In the PA, atrophy was significant at first follow-up for Gluteus Minimus (−11.8%), Obturator Internus (−46.8%) and Externus (−16%), Piriformis (−26.5%), and Quadratus Femoris (−30.4%) muscles. Recovery was not seen in any of the significantly atrophied muscles. Muscles with significant quantified fatty atrophy at final follow-up were Obturator Internus [+5.51% (DAA); +7.65% (PA)] and Obturator Externus [+5.55% (PA)]. 3/9 PA patients demonstrated abductor tendinosis, while no DAA patients demonstrated tendinosis.
Discussion
Significant atrophy for each group was seen more commonly in the anatomic regions disturbed by each approach respectively. In both approaches, muscles surgically released from their insertion showed greater atrophy, and incomplete recovery.
